US20050178282A1 - Integrated detonators for use with explosive devices - Google Patents

Abstract

A detonator assembly is provided for use in oilfield operations to detonate an explosive downhole including a capacitor discharge unit and initiator electrically connected together to form a single unit. It is emphasized that this abstract is provided to comply with the rules requiring an abstract, which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 60/521,088, entitled, “MICROELECTROMECHANICAL DEVICES,” filed on Feb. 19, 2004. This is also a continuation-in-part of U.S. Ser. No. 10/304,205, filed Nov. 26, 2002, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application Ser. No. 60/333,586, entitled, “INTEGRAL CAPACITOR DISCHARGE UNIT,” filed on Nov. 27, 2001.
BACKGROUND
• The present invention relates generally to activating devices, and more particularly to an integrated detonator for use in activating explosives.
• Explosives are used in many types of applications, such as hydrocarbon well applications, seismic applications, military armament, and mining applications. In seismic applications, explosives are discharged at the earth surface to create shock waves into the earth subsurface so that data regarding the characteristics of the subsurface may be measured by various sensors. In the hydrocarbon well context, a common type of explosive that is used includes shaped charges in perforating guns. The shaped charges, when detonated, create perforating jets to extend perforations through any surrounding casing or liner and into the surrounding formation to allow communication of fluids between the formation and the wellbore. Also, in a well, other tools may also contain explosives. For example, explosives can be used to set packers or to activate other tools.
• To detonate explosives, detonators are used. Generally, detonators can be of two types: electrical and percussion. A percussion detonator responds to some type of mechanical force to activate an explosive. An electrical detonator responds to a predefined electrical signal to activate an explosive. One type of electrical detonator is referred to as an electro-explosive device (EED), which may include hot-wire detonators, semiconductor bridge (SCB) detonators, exploding bridge wire (EBW) detonators, or exploding foil initiator (EFI) detonators.
• With certain types of electrical detonators, a local electrical source is placed in the proximity of the detonator. Such an electrical source may be in the form of a capacitor discharge unit that includes a capacitor that is charged to a predetermined voltage. In response to an activation signal, the charge stored in the capacitor is discharged into another device to perform a detonation operation. Typically, due to the relatively large amount of energy that is needed, the capacitor discharge unit can be quite large, which leads to increased sizes of housings in downhole tools that contain such capacitor discharge units. Further, because of relatively large sizes, the efficiencies of conventional capacitor discharge units are reduced due to increased resistance and inductance of electrical paths in a detonator.
SUMMARY
• In general, an improved detonator is provided that is smaller in size and that is more efficient. For example, in one embodiment, a detonator assembly includes an energy source (e.g., a capacitor) having a surface, the energy source further having electrodes. A resistor is formed on the surface of the energy source, with one end of the resistor being electrically connected to one of the electrodes.
• In some example embodiments, resistors are formed on the surface of the capacitor with thick-film deposition. For example, one type of resistor is a charging resistor. Another type of resistor is a bleed resistor that connects the two electrodes. The surface of the capacitor is used to attach electrically a switch and/or an initiator, such as an exploding foil initiator (EFI).
• In other example embodiments, an improved detonator includes an EFI, switch, capacitor, bleed resistor, transformer, and addressable chip integrated to form a monolithic unit having the size of a conventional hot-wire detonator. The monolithic unit may also include a line protection filter and an explosive.
• In another example embodiment, an improved detonator may be embedded in a tubing cutter or used to initiate the firing of a tubing cutter or jet cutter. Alternatively, an embodiment of the improved detonator may be used to initiate one or more shaped charges.
• Other features and embodiments will become apparent from the following description, from the drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A and 1B illustrate two tool strings according to some embodiments of the invention.
• FIG. 2 is a schematic electrical diagram of a detonator assembly that can be used in the tool string according toFIG. 1A or1B.
• FIG. 3 is a perspective view of the detonator assembly.
• FIG. 4 is a bottom view of the detonator assembly.
• FIG. 5 is a schematic side view of a capacitor in the detonator assembly.
• FIGS. 6 and 7 illustrate two different types of switches used in the detonator assembly ofFIG. 2.
• FIGS. 8A and 8B illustrates an embodiment of the micro-switch of the present invention as used in an integrated detonator device.
• FIG. 9 illustrates an example of the addressable functionality of an embodiment of the integrated detonator device ofFIGS. 8A and 8B.
• FIG. 10 illustrates an example of an embodiment of the voltage step-up transformer of the integrated detonator device.
• FIG. 11 illustrates an embodiment of the triggered spark gap circuitry of the integrated detonator device.
• FIG. 12 illustrates an embodiment of the piezoelectric transformer of the integrated detonator device.
• FIG. 13A-B illustrate an embodiment of the jet cutter of the integrated detonator device.
• FIGS.14A-C illustrate an embodiment of the present invention for use in detonating a shaped charge or a set of shaped charges in a shot-by-shot operation to achieve selective firing.
DETAILED DESCRIPTION
• In the following description, numerous details are set forth to provide an understanding of the present invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these details and that numerous variations or modifications from the described embodiments may be possible.
• As used herein, the terms “connect”, “connection”, “connected”, “in connection with”, and “connecting” are used to mean “in direct connection with” or “in connection with via another element”; the terms “mechanically connect”, “mechanical connection”, and “mechanically connected”, “in mechanical connection with”, and “mechanically connectiong” means in direct physical connection to form a monolithic unit such as bonded, fused, or integrated; and the term “set” is used to mean “one element” or “more than one element”; the terms “up” and “down”, “upper” and “lower”, “upwardly” and downwardly”, “upstream” and “downstream”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, such terms may refer to a left to right, right to left, or other relationship as appropriate. As used here, the terms “up” and “down”; “upper” and “lower”; “upwardly” and downwardly”; “above” and “below”; and other like terms indicating relative positions above or below a given point or element are used in this description to more clearly describe some embodiments of the invention. However, when applied to equipment and methods for use in wells that are deviated or horizontal, or when such equipment are at a deviated or horizontal orientation, such terms may refer to a left to right, right to left, or other relationship as appropriate.
• Referring toFIG. 1A, an embodiment of a tool string includes a perforating string having a perforatinggun20 and a firinghead18. The perforating string is attached at the end of acarrier line12, such as a wireline, electrical cable, slickline, tubing, and so forth. In the embodiment ofFIG. 1A, the firinghead18 includes an exploding foil initiator (EFI)detonator assembly22 according to one embodiment. As discussed below, theEFI detonator assembly22 includes an integrated assembly of a capacitor discharge unit (CDU) and EFI. It should be noted, in the embodiments using wireline or tubing to suspend the perforating string, a downhole battery may be used to supply power to the EFI.
• More generally, the integrated capacitor discharge unit has a capacitor and a charging and bleed resistor. The integrated capacitor discharge unit includes a thick-film circuit that electrically connects the capacitor and the resistor, as well as other components.
• Thedetonator assembly22 is coupled to a detonatingcord24, which is connected to a number of shapedcharges26. Activation of thedetonator assembly22 causes initiation of the detonatingcord24, which in turn causes detonation of the shapedcharges26. Detonation of the shapedcharges26 causes the formation of perforating jets from the shapedcharges26 to extend openings into the surroundingcasing10 and to extend perforation tunnels into the surroundingformation14.
• FIG. 1B shows another embodiment of the perforating string, which includes a firinghead30 and a perforatinggun32. The perforatinggun32 also includes multiple shapedcharges34. However, instead of the shapedcharges34 being connected to a detonating cord, each shapedcharge34 is associated with a respectivelocal detonator assembly36. In one embodiment, each of thedetonator assemblies36 includes EFI detonator assemblies that are configured similarly to thedetonator assembly22 ofFIG. 1A. Thedetonator assemblies36 are connected by anelectrical cable38, which provides an electrical signal to thedetonator assemblies36 to activate such detonator assemblies. The firinghead30 receives a remote command from elsewhere in thewellbore16 or from the surface of the wellbore.
• A benefit offered by the perforating string ofFIG. 1B is that the shapedcharges34 can be substantially simultaneously detonated in response to an activating signal or voltage supplied down theelectrical cable38, or fired in any desired sequence or with any desired delay. This is contrasted to the arrangement ofFIG. 1A, where detonation of successive shapedcharges26 is delayed by the speed of a detonation wave traveling down the detonatingcord24.
• Although the arrangement ofFIG. 1B includes multiple detonatingassemblies36, as compared to thesingle detonator assembly22 in the arrangement ofFIG. 1A, the small size of the detonatingassemblies36 according to some embodiments allows such detonating assemblies to be included in the perforatinggun32 without substantially increasing the size of the perforatinggun32.
• As noted above, in one embodiment, an electrical signal is provided to the firinghead22 or30 to activate the perforatinggun20 or32. However, in alternative embodiments, the activating signal can be in the form of pressure pulse signals, hydraulic pressure, motion signals transmitted down thecarrier line12, and so forth.
• Instead of perforating strings, detonator assemblies according to some embodiments can be used in other types of tool strings. Examples of other tool strings that contain explosives include the following: pipe cutters, setting devices, and so forth. Also, detonator assemblies according to some embodiments can also be used for other applications, such as seismic applications, mining applications, demolition, or military armament applications. In seismic applications, the detonator assemblies are ballistically connected to explosives used to generate sound waves into the earth sub-surface for determining various characteristics of the earths sub-surface.
• As noted above, in one embodiment, thedetonator assembly22 includes an EFI detonator assembly. EFIs include an exploding foil “flyer plate” initiator or an exploding foil “bubble activated” initiator. Other types of detonator assemblies can use other types of electrical initiators, such as exploding bridge wire (EBW) initiators and semiconductor bridge (SCB) initiators.
• As shown inFIG. 2, an electrical schematic diagram of one embodiment of adetonator assembly100. Thedetonator assembly100 can be either thedetonator assembly22 ofFIG. 1A or thedetonator assembly36 ofFIG. 1B. Thedetonator assembly100 includes a capacitor discharge unit (CDU)102, anEFI104, and a high explosive (HE)106.
• TheCDU102 includes acapacitor108, a chargingresistor110, and ableed resistor112. In addition, theCDU102 includes aswitch114 for coupling charge stored in thecapacitor108 to theEFI104 to activate theEFI104. When activated, theEFI104 produces a flyer that is propelled at usually hyper-sonic velocity and traverses agap116 to impact thehigh explosive106. In some embodiments, the flyer may be fabricated from a metal-foil or polymer-foil material. The impact of the flyer against thehigh explosive106 causes detonation of the explosive106. The explosive106 is ballistically coupled to either the detonating cord24 (FIG. 1A) or to an explosive of a shaped charge34 (FIG. 1B). In some embodiments, the internal resistance of the capacitor may be sufficient and a separate charging resistance not necessary.
• Thecapacitor108 is charged by applying a suitably high DC voltage atline118. The voltage is supplied through the chargingresistor110 into thecapacitor108. The chargingresistor110 is provided for limiting current (in case of a short in thecapacitor108 or elsewhere in the CDU102). The chargingresistor110 also provides isolation of theCDU102 from other CDUs in the tool string.
• Thebleed resistor112 allows the charge in thecapacitor108 to bleed away slowly. This is in case thedetonator assembly100 is not fired after the tool string has been lowered into the wellbore. Thebleed resistor112 prevents theCDU102 from becoming a safety hazard when a tool string withun-fired detonator assemblies100 have to be retrieved back to well surface.
• In other embodiments, other detonator assemblies with other types of energy sources (other than the capacitor108) can be employed.
• Thedetonator assembly100 includes an integrated assembly of theCDU102 andEFI104 to provide a smaller detonator assembly package as well as to improve efficiency in performance of thedetonator assembly100. Efficient CDUs need to have fast discharge times (such as nanosecond reaction rates through a low inductance path) through the EFI with low energy loss (low resistance). One way to increase the efficiency is to reduce as much as possible the inductance (L) and resistance (R) of the total circuit in the discharge loop of theCDU102. By integrating theCDU102 into a smaller package, the inductance and resistance can be reduced, thereby improving the efficiency of theCDU102.
• According to some embodiment of the invention, the chargingresistor110 and bleedresistor112 are implemented as resistors formed on a surface of thecapacitor108. Further, in some embodiments, theswitch114 is also integrated onto the surface of thecapacitor108, which further reduces the overall size of theCDU102.
• FIG. 3 shows theCDU102 according to one embodiment. Thecapacitor108 in one embodiment includes a ceramic capacitor, which has an outerceramic housing202 formed of a ceramic material. However, in other embodiments, other types of capacitors can be used. Thecapacitor108 includes a first group of one or more electrically conductive layers that are connected to one electrode, referred to as a cathode. A second group of one or more electrically conductive layers in thecapacitor108 are connected to another electrode of the capacitor, referred to as an anode. One or more layers of dielectric material are provided between the cathode and anode electrically conductive layers. The cathode layers, anode layers, and dielectric layers are provided inside theouter housing202 of thecapacitor108. As shown inFIG. 3, thecapacitor108 has afirst electrode204 andsecond electrode206. Theelectrodes204 and206 form the cathode and anode of thecapacitor108.
• Thecapacitor electrode206 is electrically contacted to anelectrical wire208. Anotherelectrical wire210 is connected to a node of the charging resistor (not shown inFIG. 3), which is formed on thelower surface212 of thecapacitor108.
• Further, theEFI104 is attached on anupper surface222 of thecapacitor108. One side of theEFI104 is connected by an electricallyconductive plate215 to theelectrode206 of thecapacitor108. The other side of theEFI104 is electrically connected to an electricallyconductive plate214, which is in turn connected to one side of theswitch114. The other side of theswitch114 is electrically connected by another electricallyconductive plate216 to thecapacitor electrode204. Electrical connections are provided by thick-film deposition, or other equivalent methods. Any number of types of small switches can be used, such as those disclosed in U.S. Pat. No. 6,385,031 and U.S. Ser. No. 09/946,249, filed Sep. 5, 2001, both hereby incorporated by reference. Also, the EFI may include an integral switch as part of its construction.
• A bottom view of theCDU102 is shown inFIG. 4. Thebleed resistor112 and chargingresistor110 are both arranged as thick-film or thin-film resistors on thelower surface212 of thecapacitor108. Oneend302 of thebleed resistor112 is electrically connected to theelectrode204, while theother end304 of theresistor112 is electrically connected to theelectrode206. Oneend306 of the chargingresistor110 is electrically connected to theelectrode204, while theother end308 of theresistor110 is electrically connected to acontact pad310. Thecontact pad310 allows electrical connection of charging theresistor110 with theelectrical wire210.
• The material and geometry (thickness, length, width) of eachresistor110 and112 are selected to achieve a target sheet resistance so that desired resistance values ofresistors110 and112 can be achieved. In other embodiments, instead of thick-film or thin-film resistors, other types of resistors that can be deposited, bonded, or otherwise formed on the capacitor housing can be used.
• To form the resistors on a surface (or surfaces) of the capacitor housing, a groove or notch can be formed in the outer surface(s) of the capacitor housing, followed by the deposition or introduction of resistance material into the groove or notch. Alternatively, a resistive material may be silk-screened or printed onto the surface(s), or other techniques may be used.
• FIG. 5 shows a schematic representation of the layers of thecapacitor108. Electricallyconductive layers312 are connected to thefirst electrode204, while electricallyconductive layers314 are connected to theelectrode206. In some embodiments, the electricallyconductive layers312 and314 are formed of a metal, such as copper, silver-palladium alloy, or other electrically conductive metal. Dielectric layers are provided betweensuccessive layers312 and314.
• According to one embodiment, the switch114 (FIG. 2) is implemented as an over-voltage switch. As shown inFIG. 6, one embodiment of theover-voltage switch114 includes a first electricallyconductive layer402 and a second electricallyconductive layer406. Interposed between the electricallyconductive layers402 and406 is an insulating (dielectric)layer404. In one example implementation, the electricallyconductive layers402 and406 are formed of copper or other electrically conductive metal. In one example implementation, the insulatinglayer404 is formed of a polyimide material.
• The insulatinglayer404 has a thickness and a doping concentration controlled to cause theswitch114 to activate at a selected voltage difference between electricallyconductive layers402 and406. Once the voltage crosses over some predefined threshold level, the insulatinglayer404 breaks down to electrically connect the first and second electricallyconductive layers402 and406 (thereby closing the switch114).
• Optionally, the breakdown voltage of the insulatinglayer404 can be controlled by having the geometry of overlapping electricallyconductive layers402 and406 be somewhat pointed to increase the potential gradient at the points. Further, depositing a hard metal such as tungsten on contact areas of the first and second electricallyconductive layers402 and406 can prevent burn-back of the electrically conductive layers. The contact areas are provided to electrically connect the electricallyconductive layers402 and406 to respective wires. The hardened metal also provides for a more efficient switch. Also, for increased efficiency, the gap distance between points is made small, such as on the order of a few thousands of an inch.
• FIG. 7 illustrates another type ofswitch114. This alternative switch is a triggered switch that adds another electrically conductive layer that is connected to a trigger voltage. As shown inFIG. 7, thetriggered switch114 includes top and bottom electricallyconductive layers410 and414, in addition to an intermediate electricallyconductive layer412. Insulatinglayers416 and418 are provided between successively electrically conductive layers. In operation, a high voltage (reference to ground) with a fast rise time is applied to thetrigger anode412. The trigger voltage has sufficient amplitude to cause the insulatinglayers416 and418 to break down to allow conduction between the top and bottom electricallyconductive layers410 and414.
• In other embodiments of the detonator of the present invention, micro-switches may be integrated to form a small, low-cost detonator utilizing Exploding Foil Initiator technology. For example, in one embodiment, a micro-switchable EFI detonator is small enough to fit inside a standard detonator housing, thereby simplifying logistics and packaging, easing assembly, and improving overall reliability while replacing the less safe hot-wire detonator. A “micro-switch” may be used as disclosed in U.S. Ser. No. 10/708,182, filed Feb. 13, 2004, which is hereby incorporated by reference. Such a micro-switch may include, but is not limited to, a microelectromechanical system (MEMS) switch, a switch made with microelectronic techniques similar to those used to fabricate integrated circuit devices, a bistable microelectromechanical switch, a spark gap switch, a switch having nanotube electron emitters (e.g., carbon nanotubes), a metal oxide silicon field-effect transistor (MOSFET), an insulated gate field-effect transistor (IGFET), and other micro-switching devices.
• With respect toFIGS. 8A and 8B, in general, an embodiment of the present invention may include a small,monolithic detonator800 with all components integrated into a single unit. The components may include, but are not limited to: an integratedcapacitor discharge unit808 including a charging resistor and bleeder resistor that are fused or bonded together with a micro-switch and an initiator (e.g., an EFI, EBW, SCB, hot-wire, or other initiator), an initiating explosive806, a conventional explosive804 (e.g., PETN, RDX, HMX, CL-20, HNS, NONA and/or other explosive), a step-uptransformer810 for receiving a low voltage input and stepping up to a high voltage output, and anaddressable chip812. In another embodiment, a microchip may be employed for ease of design. The resultant size of theintegrated detonator800 is small enough to be packaged inside astandard detonator housing802 and may receive power via astandard plug814.
• An embodiment of thedetonator800 has a size and shape substantially equal to that of a standard cylindrical hot-wire detonator. For example, some standard hot-wire detonators have a cross-sectional diameter of approximately 0.28 inches. In another example, an embodiment of thedetonator800 may have the same diameter as the detonating cord24 (FIG. 1A) to which the detonator is coupled. This relatively small-sized detonator may be desirable over large-sized prior art detonators, which generally consist of a bulky capacitor discharge unit (CDU) (including an EFI, gas-tube switch, bleeder resistor, and capacitor), together with a multiplier, smart electronics, and explosive packaged in a relatively large housing having a 0.75 inch diameter cross section. The relatively large size of these prior art detonators limits their application and field use, as well as increases the cost of manufacturing. While this embodiment of the detonator of the present invention has a cross-sectional diameter of approximately 0.28 inches, it is intended that other embodiments may include integrated detonators having other cross-sectional diameters.
• Besides having a smaller overall size, embodiments of thedetonator800 of the present invention may include various advantages over prior art detonators for facilitating safe arming and firing. Some embodiments have an added advantage of firing at lower voltage. For example, the detonator may be configured to respond to a firing voltage of as low as approximately 30 volts. Moreover, some embodiments of thedetonator800 include a radio frequency identification (RFID) tag to facilitate secure arming and triggering functions, as well as providing for identification and inventory control. Additionally, embodiments of the detonator may be rated for operation in temperatures up to approximately 340° F. Higher temperatures (up to approximately 500° F.) may be achieved with the inclusion of a thermal-delay vessel. Still other embodiments of the detonator may be fluid desensitized, radio frequency safe, and/or protected from unintended surface power.
• With respect toFIGS. 8A and 8B, an embodiment of thedetonator assembly800 may include a capacitor808 (cylindrical or rectangular) formed from a dielectric/polarized material having a built-in (e.g., thick film) bleed resistor on one end and having a EFI and micro-switch mounted on the other end. The EFI may be fused or bonded to thecapacitor808 and a micro-switch for activating the EFI may be located on the same substrate as the EFI or, alternatively, on a separate substrate. The micro-switch may be an over-voltage type in a miniaturized chamber, and, in some embodiments, the micro-switch may be enhanced by carbon nanotubes as described in U.S. Ser. No. 10/708,182.
• Still with respect toFIGS. 8A and 8B, an embodiment of thedetonator assembly800 may also include a step-uptransformer810 as illustrated in the circuit diagram ofFIG. 10. The transformer may be fabricated such that it is fused or bonded directly to thecapacitor800. The transformer may be capable of receiving a low-voltage input (e.g., 5 to 30 volts) and stepping up to a high voltage output (e.g., 1400 volts) via a separate high-voltage diode. In some embodiments, the transformer may be fabricated from a metallic, ceramic, or ceramic-ferrite material having high magnetic permeability characteristics using a conventional wire wind process or low temperature co-fired ceramic (LTCC) process using silk-screened conductor coils.
• Further with respect toFIGS. 8A, 8B, and10, an embodiment of thedetonator assembly800 may also include anaddressable chip812. Theaddressable chip812 may facilitate control selectivity and provide added safety against accidental firing. The inclusion of anaddressable chip812 is made possible due to the low-voltage input of thetransformer810, which facilitates packaging addressability into thechip812. Theaddressable chip812 may be designed for standard CMOS integration with 5-volt or 3.3-volt operation using logic state machine. Moreover, some embodiments of the chip may be configured to have built-in digital signal processing for improved down-link signal recognition and an up-link using a bi-phased current loop.
• In operation, an embodiment of thechip812 facilitates the integration of electronic addressable functions such as: (1) uniquely identifies and selects one or more explosive initiators from a set of initiators; (2) enables the selective charging and firing of the one or more initiators and allows programming of a specific time delay; (3) enables sleep mode, or inactive state, timing delay mode, arm and fire modes and switching modes to open or close reselected circuit; (4) enables sensor mode to monitor signal from sensors (e.g., pressure, temperature, tilt angle, current, voltage, etc.); and/or (5) enables disconnect mode to disconnect bottom-fired initiators from the rest of the string by sensing a sufficient rise in current, with following progression. An illustration of the above-identified functionality is shown inFIGS. 9 and 10. It is intended that the addressable chip may be configured to perform one or all of these functions and others.
• For example, an embodiment of the detonator having an addressable chip may provide a method to trigger the detonator based on an internal timer or external trigger mechanism. Furthermore, the addressable chip may include common commands to start multiple timers in a detonation string. Each timer could be preset to provide precise delays among the string. This precise control of time delays among the string enables the production of beneficial dynamic pressure-time characteristics. For example, U.S. Pat. No. 6,598,682—regarding dynamic pressure underbalance and overbalance control—discloses a system to optimize the performance of the perforation process as well as to limit the collateral damage of the gun system and other wellbore equipment by limiting the peak over-pressure and destructive pressure wave resonances and pressure wave reinforcements.
• With respect toFIG. 11, another embodiment of the present invention provides a method to generate a trigger pulse by stepping up the slapper capacitor voltage using a second transformer of a type including, but not limited to, low temperature co-fired ceramic, LTCC, tape wound, air core, and/or super-cooled amorphous core. This trigger pulse enables controlled and accurate timing of the detonator's firing and more efficient charging of the slapper capacitor because it can be fully charged before it is triggered to fire the detonator. Whereas the spark gap fires whenever its threshold voltage is exceeded, the trigger circuit and trigger electrode provides alternatives for the controlled firing of the spark gap—for example, upon command from the surface, upon completion of a pre-programmed time delay, or, if a pressure sensor measurement is also employed, upon attainment of a pre-set threshold of pressure or pressure profile with time.
• Another embodiment of the present invention provides a method to generate a trigger pulse by supplying voltage generated using a piezoelectric mechanical transformation, as shown schematically inFIG. 12. Compared to conventional transformers, this is an alternative triggering method achieves the benefits described above for more accurate and efficient detonator firing. This piezoelectric method also offers advantages of lower components parts count, smaller package size, and lower voltage drive by the integrated circuit.
• The small size of the present invention enables the novel and advantageous ability to initiate the firing of a jet cutter from its geometric center. As illustrated inFIGS. 13A and 13B, the jet cutter includes an explosive material formed intimately against a metallic liner. The liner is configured substantially about a central axis substantially to the shape of a conical frustum between a normally truncated apex and a normally truncated base. The EFI (or other initiator) with its associated CDU is positioned such that its explosive pellet is located at the center of the cutter. The EFI/CDU is attached by a pair of simple wires through the explosive center. Alternately, as shown inFIG. 13B, the EFI may be attached by a low inductance, high voltage cable to an external CDU, which is initiated by an electrical signal. In any case, the benefits of the present invention include achievement of a centered jet cutter initiation, which translates to optimum cutter performance, no external electronics or detonating cord, only simple wires from the center of the cutter, and the improved safety of this RF safe and addressable detonator.
• Moreover, with respect to FIGS.14A-C, instead of being embedded in a jet cutter, embodiments of the EFI/CDU unit may be substantially embedded in or connected directly to a shaped charge having an explosive material having a truncated base and formed intimately against a liner. As with the jet cutter, the EFI/CDU may be attached by a pair of simple wires (FIG. 14B), or, alternatively, the EFI may be attached by a low inductance, high voltage cable to an external CDU, which is initiated by an electrical signal (FIG. 14C). Either of these arrangements may be used in detonating a series of shaped charges in a shot-by-shot operation to achieve selective firing (FIG. 14A).
• While the invention has been disclosed with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover such modifications and variations as fall within the true spirit and scope of the invention.

Claims (48)

1. A detonator assembly, comprising:

a capacitor;

an initiator mechanically and electrically connected to the capacitor;

a transformer mechanically and electrically connected to the capacitor; and

an addressable chip mechanically and electrically connected to the transformer,

wherein the capacitor, initiator, transformer, and addressable chip form an integrated detonating unit.

2. The detonator assembly ofclaim 1, further comprising a capacitor discharge unit, the capacitor discharge unit comprising the capacitor and a resistor.

3. The detonator assembly ofclaim 2, wherein the capacitor discharge unit further comprises a thick-film circuit that electrically connects the capacitor and the resistor.

4. The detonator assembly ofclaim 3, wherein the resistor comprises a bleeder resistor formed by thick-film deposition, the bleeder resistor adapted to bleed charge form the capacitor.

5. The detonator assembly ofclaim 4, wherein the resistor comprises a charging resistor formed by thick-film deposition, the charging resistor adapted to receive a charging voltage for the capacitor.

6. The detonator assembly ofclaim 2, wherein the capacitor discharge unit further comprises an integrated micro-switch, the micro-switch adapted electrically to couple the charge from the capacitor to the initiator when activated.

7. The detonator assembly ofclaim 6, wherein the micro-switch comprises one of a microelectromechanical system switch, a bistable microelectromechanical switch, a spark gap switch, a switch having nanotube electron emitters, a MOSFET, and an IGFET.

8. The detonator assembly ofclaim 1, wherein the initiator comprises one of a semiconductor bridge, exploding bridge wire, and exploding foil initiator.

9. The detonator assembly ofclaim 2, wherein the initiator comprises an exploding foil initiator fused directly to the capacitor discharge unit.

10. The detonator assembly ofclaim 1, further comprising an explosive proximate the initiator.

11. The detonator assembly ofclaim 2, wherein the capacitor is fabricated from a dielectric ceramic material.

12. The detonator assembly ofclaim 2, wherein the resistor is selected from the group consisting of a thick-film resistor and a thin-film resistor.

13. The detonator assembly ofclaim 1, wherein the transformer is a piezoelectric transformer.

14. The detonator assembly ofclaim 1, further comprising a second transformer adapted to generate a trigger pulse to fire the initiator.

15. The detonator assembly ofclaim 1, wherein the addressable chip is adapted to identify one or more initiators from a set of initiators.

16. The detonator assembly ofclaim 15, wherein the addressable chip is adapted to selectively charge one or more initiators from the set of initiators.

17. The detonator assembly ofclaim 15, wherein the addressable chip is adapted to selectively delay for a predetermined time the charging of one or more initiators from the set of initiators.

18. The detonator assembly ofclaim 15, wherein the addressable chip is adapted to selectively fire one or more initiators from the set of initiators.

19. The detonator assembly ofclaim 15, wherein the addressable chip is adapted to selectively delay for a predetermined time the firing of one or more initiators from the set of initiators.

20. The detonator assembly ofclaim 1, wherein the addressable chip is adapted to inactivate the initiator.

21. The detonator assembly ofclaim 1, wherein the addressable chip is adapted to activate a sensor.

22. The detonator assembly ofclaim 21, wherein the sensor is a pressure sensor.

23. The detonator assembly ofclaim 21, wherein the sensor is a temperature sensor.

24. The detonator assembly ofclaim 21, wherein the sensor is a tilt-angle sensor.

25. The detonator assembly ofclaim 21, wherein the sensor is a current sensor.

26. The detonator assembly ofclaim 21, wherein the sensor is a voltage sensor.

27. The detonator assembly ofclaim 21, wherein the sensor is a radio frequency sensor adapted to detect radio frequency identification tags.

28. The detonator assembly ofclaim 1, wherein the addressable chip is adapted to disconnect a bottom-fired initiator from a string of initiators.

29. The detonator assembly ofclaim 1, further comprising a housing adapted to hold the detonating unit.

30. The detonator assembly ofclaim 29, wherein the housing has an outer diameter of approximately 0.28 inches.

31. The detonator assembly ofclaim 29, wherein the housing is adapted to couple with a detonating cord having a predetermined diameter.

32. The detonator assembly ofclaim 31, wherein the housing has an outer diameter substantially equal to the diameter of the detonating cord.

33. A method of fabricating an integrated detonator, comprising:

providing a capacitor discharge unit;

mechanically and electrically connecting a transformer to the capacitor discharge unit;

mechanically and electrically connecting an addressable chip to the transformer; and

electrically connecting a micro-switch and initiator to the capacitor discharge unit.

34. The method ofclaim 33, wherein providing a capacitor discharge unit comprises mechanically and electrically connecting a resistor and a capacitor.

35. The method ofclaim 33, further comprising providing an explosive proximate the initiator.

36. A jet cutter, comprising:

a first explosive material formed intimately against a metallic liner; and

a detonator assembly substantially embedded in the first explosive material, the detonator assembly comprising an initiator, a capacitor, and a second explosive material proximate the initiator.

37. The jet cutter ofclaim 36, wherein the initiator and capacitor are fused or bonded together to form a single unit.

38. The jet cutter ofclaim 36, wherein the capacitor is located external to the first explosive material, and wherein the initiator and capacitor are electrically connected together by a cable.

39. A shaped charge, comprising:

a first explosive material formed intimately against a metallic liner; and

a detonator assembly comprising an initiator, a capacitor, and a second explosive material proximate the initiator,

wherein the second explosive material is in direct contact with the first explosive material.

40. The shaped charge ofclaim 39, wherein the initiator and capacitor are mechanically connected to form an integrated unit.

41. The shaped charge ofclaim 39, wherein the capacitor is located external to the first explosive material, and wherein the initiator and capacitor are electrically connected together by a cable.

42. A detonator assembly, comprising:

a capacitor discharge unit, the capacitor discharge unit comprising a charging resistor, a bleeder resistor, and a capacitor mechanically and electrically connected together;

an initiator mechanically and electrically connected to the capacitor discharge unit, the initiator selected from the group consisting of an exploding foil initiator, an exploding bridge wire, a semiconductor bridge, and a hot wire;

a micro-switch mechanically and electrically connected to the capacitor discharge unit and the initiator;

an initiating explosive proximate to the initiator; and

a housing adapted to hold the capacitor discharge unit, the initiator, the initiating explosive, and the micro-switch together to form an integrated detonating unit.

43. The detonator assembly ofclaim 42, further comprising:

an addressable chip;

a protection filter electrically connected to the addressable chip; and

a first transformer mechanically and mechanically and electrically connected to the addressable chip and the capacitor discharge unit,

wherein the addressable chip, protection filter, and first transformer are located within the housing.

44. The detonator assembly ofclaim 43, further comprising a second transformer electrically connected to the micro-switch, the second transformer adapted to generate a trigger pulse to fire the initiator.

45. A method for use in a wellbore, comprising:

providing a capacitor, an initiator, a micro-switch, an addressable chip, a transformer, and an initiating explosive mechanically and electrically connected together to form an integrated detonating unit;

connecting the integrated detonating unit to an explosive tool;

deploying the explosive tool in the wellbore; and

firing the initiator to activate the explosive tool.

46. The method ofclaim 45, wherein the explosive tool is a jet cutter.

47. The method ofclaim 45, wherein the explosive tool is a shaped charge.

48. The method ofclaim 47, further comprising:

selecting the shaped charge to fire from a plurality of shaped charges deployed in the wellbore.

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